1. Field of the Invention
This invention relates to a system for cooling electronics, and more specifically this invention relates to a compact system and method for cooling hybrid vehicle electronics using only one radiator.
2. Background of the Invention
Hybrid vehicle electronics have become more sophisticated. As a result, the use of wide-bandgap semiconductors will increase. Wide-bandgap semiconductors permit devices to operate at much higher voltages, frequencies and temperatures than conventional semiconductor materials. This allows for more powerful electrical mechanisms to be built which are cheaper and more energy efficient.
“Wide-bandgap” refers to higher voltage electronic band gaps significantly larger than one electron volt (eV). The exact threshold of “wideness” often depends on the context, but for common usage, “wide” bandgap typically refers to material with a band gap of at least 3 eV, significantly greater than that of the commonly used semiconductors, silicon (1.1 eV) or gallium arsenide (1.4 eV).
Wide-bandgap materials are often utilized in applications in which high-temperature operation is important. The higher energy gap gives the devices the ability to operate at higher temperatures. However, a junction temperature of between 150° C. and 175° C. should be maintained under the semiconductors to prevent electronics malfunction. This cannot be accomplished with 105° C. coolant used in standard radiators.
Automotive examples of wide-bandgap devices include traction drive components, battery chargers (for plug in hybrid electric vehicles, PHEVs), boost converters (for stepping up battery voltages higher than the battery capacities), inverters (for converting DC to AC for phased power to traction motors and generators), and bi-directional DC-DC converters (to shuttle power among buses to operate lighting, brake assist, power steering, etc.).
State of the art power electronic semiconductors in hybrid vehicles attempt to address high temperatures using multiple heat exchangers or radiators. Typical heat sink configurations consist of multiple layers of materials, starting with the semiconductors, followed by a copper thermal spreader, one or more layers of a thermal interface material (TIM), and flow channels for the liquid coolant.
FIG. 1 is a perspective view of a prior art cooling configuration, that configuration designated as numeral 9. One or a plurality of semiconductors 12 are supported on a thermal spreading substrate 14. The thermal spreading substrate 14 is supported by one or a plurality of TIM 16. This TIM 16 is in physical contact with flow channels 18 adapted to receive coolant fluids.
Each of the layers below the semiconductors of FIG. 1 has a resistance to heat transfer. The largest of these resistances are the TIMs 16 and the coolant fluid. Coolant fluids exhibit high resistance to heat transfer due to their laminar flow characteristics. Such poor laminar flow heat transfer rates require that a second radiator (using 75° C. coolant) be used in hybrid electric vehicles to cool the power electronics. As such, state of the art hybrid vehicle cooling systems utilize two separate radiators, one for the internal combustion engine, and a second one for the electronics. This second radiator and associated plumping adds cost and weight to the vehicle while reducing available space for other components.
A need exists in the art for an electronics cooling system and method that does not employ multiple radiators. The system and method should eliminate or substantially reduce the thermal resistance now plaguing state of the art coolant-side fluid dynamics, such that the system and method eliminates the potential of a TIM reaching a CHF condition. The system and method should maintain the electronics side at no more than approximately 175° C., given power production rates of state of the art chips of about 100 W/cm2, while minimizing pumping power requirements.